Data decoding in various wireless communication systems usually needs to use channel estimation (CE) to achieve coherent decoding. Common channel estimation generally utilizes a wireless transmitting device to transmit a reference signal known by a given wireless receiving device, and then the wireless receiving device estimates the channel frequency response (CFR) of the wireless channel based on the received reference signal.
In order to increase the communication capacity, the wireless transmitting device may distribute multiple reference signals to the same subcarrier in a superimposed manner, and use multiple antennas to transmit these reference signals. Because the multiple reference signals are transmitted on the same subcarrier, interference will occur between these superimposed reference signals. In this way, the wireless receiving device cannot distinguish these reference signals from the received signal and thus cannot perform channel estimation according to the respective reference signals. It is known that cover code can be adopted to solve the aforesaid problem. Adopting cover code is to utilize a specific code to cover a certain reference signal so as to reduce the interference generated by the reference signal superimposed with another reference signal.
Taking the 5th Generation New Radio (5G NR) communication system as an example, the cover code adopted is an alternative sequence vector, e.g., a vector represented as [1, −1, 1, −1, 1, . . . , 1, −1]. However, under the influence of wireless channel, it is possible that such an alternative sequence cannot completely reduce the interference between the multiple superimposed reference signals, and thus the wireless receiving device still cannot effectively distinguish these reference signals from the received signals. In this case, error floor will inevitably occur to the channel estimation, thereby influencing the decoding performance of the wireless receiving device.
Accordingly, it is important in the art to enable the wireless receiving device to more effectively distinguish the multiple reference signals transmitted on the same subcarrier from the received signals.